Naloxegol, also known as and NKTR-118 and AZ-13337019, is a peripherally-selective opioid antagonist for the treatment of opioid-induced constipation. It was approved in 2014 in adult patients with chronic, non-cancer pain. Chemically, naloxegol is a pegylated (polyethylene glycol-modified) derivative of α-naloxol. Specifically, the 5-α-hydroxyl group of α-naloxol is connected via an ether linkage to the free hydroxyl group of a monomethoxy-terminated n=7 oligomer of PEG.